Conventional multi-turn encoders typically comprise a plurality of shafts, gears, and associated code wheels, or the like, as exemplified by U.S. Pat. No. 5,640,007 to Talbott, U.S. Pat. No. 6,542,088 to Bielski, U.S. Pat. No. 6,577,985 to Scalf, and U.S. Pat. No. 6,683,545 to Strasser, each of which is incorporated herein by reference in its entirety. Such encoders tend to have a relatively high number of parts, relatively complicated assembly, a relatively large dimension along the axial direction, and a relatively high cost. An absolute encoder that uses a planetary gear shaft-speed reduction system to accept a high-speed shaft input and drive a low-speed shaft is described in U.S. Pat. No. 6,732,438 to Ito. The absolute encoder includes a high-speed shaft encoder and a low-speed shaft encoder. However, this absolute encoder also suffers the limitations and drawbacks outlined above.
A relatively simple and low cost multi-turn potentiometer using a planetary gear system is described in U.S. Pat. No. 6,732,438 to Enzinna. However, the angular measuring accuracy and reliability of such a potentiometer system are insufficient for many applications. Thus, a multi-turn encoder that can overcome the foregoing problems and disadvantages, individually or in combination, is desirable.